The invention relates to an X-ray device which includes a C-arm carrying an X-ray source and an X-ray detector, and also includes a suspension device which carries the C-arm via a joint, the X-ray source and the X-ray detector being rotatable about a propeller axis which extends through the joint.
X-ray devices of this kind are generally known and are frequently used for medical diagnostic imaging. The patient to be examined is then usually positioned horizontally on a patient table. In order to form X-ray projections, notably for angiography, the projection direction can be varied within given limits. The X-ray source and the X-ray detector are thus rotatable in an angular range about the longitudinal axis of the patient; the angle between the projection direction and the longitudinal axis of the patient is adjustable and the suspension device carrying the C-arm is usually anchored in space in such a manner that it is rotatable in an angular range about a vertical axis. As a result, the X-ray source can occupy successive positions in time so as to describe given trajectories, for example, a semi-circular trajectory where the projection direction varies accordingly. Display in a fast succession of the projections thus obtained on a display screen offers the physician a better idea of the three-dimensional situation, for example of the vessels examined. Three-dimensional images of the volume examined can also be calculated from these projections.
In the known X-ray devices, however, the possibilities for adjustment and movement of the X-ray source are constrained by the mechanical construction of the X-ray device. For example, notably the position of the so-called propeller axis, i.e. the axis extending through the joint linking the C-arm to the suspension device, can change only in a horizontal plane extending through the patient. This constraint also limits the course of the trajectories that are possible. For example, in the known X-ray devices it is not possible for the X-ray source to describe a trajectory in the form of a full circle around the patient or in the form of two tilted full circles around the patient. To some extent this is also due to the fact that the joint linking the C-arm to the suspension device is not suitably designed, but essentially to the fact that the overall mechanism of the X-ray device, notably the weight of the C-arm, does not permit such motions.
Therefore, it is an object of the invention to provide an X-ray device which is mechanically stable and is capable of realizing different trajectories.
On the basis of an X-ray device of the kind set forth this object is achieved by means of an X-ray device.
The invention is based on the recognition of the fact that the trajectories that can be described in the known X-ray devices are also constrained by the fact that the position of the propeller axis can be changed in one plane only. Therefore, according to the invention the X-ray system, notably the C-arm, the joint and the suspension device are to be designed in such a manner that the position of the propeller axis can also be changed in other directions. When suitably constructed, the mechanism of the C-arm may also be simpler and notably the weight of the C-arm may be lower, so that the desired trajectories can be realized for the X-ray tube.
Further advantageous embodiments of the invention are disclosed in the further Claims.
Particularly advantageous is a further embodiment in which the suspension device and/or a holding device carrying the suspension device have a construction in the form of an arc of a circle. In this embodiment all axes of rotation of the X-ray device, notably also the propeller axis through the so-called isocenter in which the object to be examined is arranged and wherethrough the projection lines (the connecting line between X-ray source and X-ray detector) also extend, can be simply made to intersect. To this end, the suspension device or the holding device preferably exhibits the same curvature as the C-arm.
In a preferred embodiment of the invention the suspension device is constructed in such a manner that the C-arm and the joint are rotatable about a horizontal axis of rotation which extends perpendicularly to the propeller axis. As a result, in comparison with the known X-ray devices the C-arm can be constructed so as to be significantly simpler and above all lighter, because it need carry only the X-ray source and the X-ray detector but no further mechanical elements which enable the rotary motion about the axis of rotation in the known X-ray devices. This functionality is provided by the suspension device in this further embodiment.
Furthermore, the joint is constructed as a revolute joint in such a manner that the X-ray source and the X-ray detector can be rotated 360xc2x0 around the axis of rotation an arbitrary number of times. This can be realized notably in the described further embodiment of the invention in which the C-arm can have a particularly light construction.